Vol 64, No 8 (2019)

The review of methods of calculation of irregular waveguides is presented. The history of the appearance of waveguide equations and methods for solving systems of waveguide equations for various types of transmission lines is observed.

Approximation of microwave transmission line is used to study synthesis of impedance transformers for super-wideband two-section antenna arrays. Several variants of a complicated nonmonotonic impedance transformer (two-section array that represents two monotonic or nonmonotonic and monotonic transformers) are considered. Parameters of step transformers are synthesized in the approximation of small coefficients of reflection from steps of characteristic impedances of the transmission line. The method for synthesis is extrapolated to continuous transformers. Variants of construction of two-section antenna arrays are compared, and the error of the approximate synthesis method is estimated.

A method for synthesis of controlled zeros in the radiation pattern along the jamming direction is proposed for a plane phased array antenna. To solve the problem, it is suffice to calculate the amplitude–phase distribution for only one row (column) of antenna elements located on the array at the mesh points of rectangular or hexagonal cells.

The modulating functions (MFs) of GBOC signals (generalized BOC signals) of prospective satellite radio navigation systems, such as Galileo (EU), GPS (United States), and BeiDou (China), are considered. A method for calculating the correlation functions (CFs) of single elements of MFs of GBOC signals based on inverse Fourier transform (FT) of their energy spectra is proposed. The method is based on representation of the energy spectrum as a weighted algebraic sum of the cosines of angles determined by characteristic points of the sine symbol of MFs of GBOC signals (CF breakpoints). According to the method, analytical expressions for the CFs of single elements of MFs of GBOC signals are obtained as the inverse FT of energy spectra with a pulse multiplicity coefficient \({{N}_{{\text{p}}}}\) = 2 and 4 for different duty cycle values ρ, where \(\rho \)\( \in \) [0, 1]. In some cases, calculation of the CFs of GBOC signals based on the inverse FT of energy spectra is preferable (in particular, in terms of labor-intensity) compared with the method of obtaining CFs based on its general definition.

An experiment to study the multipath propagation of ultra-wideband (UWB) chaotic radio pulses of the microwave range through a wireless channel inside buildings is described and its results are analyzed. The limitations that multipath propagation imposes on the link margin of UWB communication lines on chaotic radio pulses are established.

An alternative circuit configuration for realizing an electronically adjustable floating capacitance multiplier is presented in this article. By consisting of only one fully balanced-voltage differencing buffered amplifier (FB-VDBA), one resistor and one capacitor, the presented multiplier circuit is canonical structure, and does not require any critical element matching constrain. The equivalent value of the simulated capacitance is adjustable by tuning the bias current of the FB-VDBA. The effect of the FB-VDBA non-idealities on the realized capacitance has been considered in detail. The proposed floating capacitance multiplier has been utilized, as an example application, in the design of a second-order RLC band-pass filter. To support the theory, some computer simulations with PSPICE software are also reported.

We report the results of the theoretical study and experimental development of a technique for fabricating low-temperature co-fired ceramics used in microwave devices and the results of the calculation and fabrication of two ceramic slips made with different types of glass for the formation of low-temperature co-fired green ceramic tape. It has been experimentally confirmed that the developed binding composition exhibits properties similar to those of Ferro A6M ceramics. It is demonstrated that the glass-forming components BaO and PbO make it possible to increase the permittivity and decrease the dissipation factor of the entire material. The main characteristics of the obtained material are compared with those of low-temperature co-fired Ferro A6M ceramics.

In this paper, we present the results of studies of the heat capacity of single-crystal garnets Er_3 ‒ xTm_xAl₅O₁₂ (x = 0, 1, 2, 3) in magnetic fields of up to 9 T and in the temperature range 1.9–220 K. The temperature dependences of the heat capacity are approximated using the sum of the contributions of Schottky anomalies associated with magnetic Er³⁺ and Tm³⁺ ions and the Debye and Einstein lattice contributions. Entropy and magnetic entropy are calculated using the heat capacity data. With an increase in the magnetic field, entropy is shown to decrease. This indicates the possibility of using the studied garnets in the adiabatic demagnetization method.

The results of a theoretical analysis and computer simulation of the capacity of a MIMO system under the conditions of spatially correlated fadings are presented. As a result of the theoretical analysis, approximate analytical expressions are obtained for the capacity of the MIMO system radio channel. These expressions make it possible to analytically derive quantitative estimates of the capacity of the MIMO system radio channel for various antenna configurations under the conditions of spatially correlated fadings. The results of the theoretical analysis are confirmed by simulation.